Electric resistance heater



Dec. 30, 1952 T. W. GLYNN ELECTRIC RESISTANCE HEATER Filed June 21, 19512 SHEETS-SHEET l IN V EN TOR. M50002: (7X61. YNN

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ELECTRIC RESISTANCE HEATER Filed June 21, 1951 2' SHEETS-SHEET 2'HTTOPNEXi Patented Dec. 30, 1952 UNITED STATES PATENT OFFICE ELECTRICRESISTANCE HEATER Theodore W. Glynn, Kingsport, Tenn., assignor to BlueRidge Glass Corporation, Kingsport, Tenn., a corporation of New YorkApplication June 21, 1951, Serial No. 232,746

Claims. 1

This invention relates to electric resistance heaters, and moreparticularly, to those in which an electric heating element covers oneside of an upright glass plate for space heating.

Such heaters are Well known and are generally mounted so that they canbe set upright on the floor or attached to a wall of a room. Due toconvection, the top portions of such plates always are hotter than thebottom portions. The heating elements of the heaters have been a singleelectrical conductor made of aluminum or other metal having the desiredelectrical resistance for producing heat. The conductor usually isformed by spraying the resistance material on the glass plate. Since theresistanace of the heating element becomes greater as the temperature ofthe plate increases, and the top portion becomes hotter than the bottomportion due to convection, the top portion is caused to have a greaterresistance than the bottom portion. With a series circuit, in accordancewith Ohms law, that portion having the greater resistance will developthe most heat. Thus, the convection and the increase in resistance ofthe top portion both cause a considerable temperature difference betweenthe top and bottom of the plate.

It is among the objects of this invention to provide an electricresistance heater in which the temperature difference between the topand bottom of the plate is reduced, in which the maximum temperature ofany part of the plate and the average temperature of its upper half arereduced at the same time that the average temperature of the lower halfof the plate is increased, in which a higher wattage can be put into theplate for a given maximum temperature of any part of plate thanheretofore, and in which high voltage differences are avoided in thehottest part of the plate.

g In accordance with this invention, a heating element covers most ofone side of an upright glass plate. The ends of the heating element areconnected to a pair of electric terminals. The heating element is formedfrom a plurality of electrical conductors having the desired electricresistance, which are connected in parallel between the terminals. Eachof the conductors covers a different area of the plate, the areas beingdisposed one above the other. Although three or more conductors can beused in some cases with better results than two, for most practicalpurposes two conductors are sufiicient, one of them coveringsubstantially the upper half of the plate and the other one coveringonly the lower half of the plate. The conductors preferably extendeither back and forth across the plate in vertically spaced lengths orup and down the plate in horizontally spaced lengths.

The invention is illustrated in the accompanying drawings, in which Fig.1 is a view of one side of an upright electric resistance heater; andFigs. 2, 3, 4 and 5 are diagrammatic side views of four modifications ofthis invention.

Referring to Fig. 1 of the drawings, a rectangular panel or plate I oftempered glass of the type generally used for an electric resistancetype of space heater is adapted to be mounted in a frame or othersupport of well known form which can be set on the floor or hung on aWall. Since the frame forms no part of the invetnion, it is notdisclosed. Mounted on one side of the glass plate is an electric heatingelement which is formed from at least two electric conductors 2 and 3integrally connected in parallel to a pair of terminals 4 and 5, mostsuitably disposed at the bottom of the plate substantially midwaybetween its ends. Soldered to these terminals are metal sleeves 6, inwhich wires 1 are fastened for connecting the heating element in anelectric circuit, such as the usual volt household circuit.

The conductors are formed from electrical re sistance material,preferably aluminum or aluminum alloy sprayed on the surface of theplate in a predetermined pattern. The pattern is such that with twoconductors or resistors, one of them covers substantially the upper halfof the plate, while the other covers only the lower half. The twoconductors have substantially the same resistance when cold. The upperconductor 2 may be somewhat longer than the lower one, although notnecessarily so. The upper conductor extends from terminal 4 along thebottom of the plate to a point near the adjacent right hand corner. Theconductor then extends straight up the plate to a point near its top andthen straight across the plate to a point near its opposite end. Fromthere the conductor extends down a very short distance and then backacross the plate. The conductor continues to extend back and forthacross the plate in this zigzag fashion until it reaches a point abouthalf way down the plate at the left hand end of the plate. The upperhalf of the plate therefore is traversed by a considerable number ofvertically spaced parallel lengths of conductor 2 in the form ofhorizontal bars. From the left hand end of the lowest bar, conductor 2extends down the end of the plate to its bottom and then straight acrossto terminal 5, thus'completing a circuit.

I'he other conductor 3 covers the area of the plate that is surroundedby the first conductor. This is substantially the lower half of theplate. Thus, the lower conductor extends from terminal 4 horizontallytoward the adjacent end of the plate and then upward a short distanceand back toward the same terminal. If the terminal is too high for theconductor to extend across it, the conductor then extends back to theright hand end of the plate again and then back across substantially thefull length of the plate. From there conductor 3 extends back and forthacross the plate in the same way as the other conductor to formvertically spaced parallel lengths or bars. The upper bar is directly.below the lowest bar of the upper conductor, and its left hand end isconnected by a vertical portion to a lower portion that extends back andforth between the vertical portion and terminal 5 until conductor 3connects with that terminal.

When this heater is plugged into an electric circuit, the top half ofthe plate will become hotter than the lower half, due to convection. Thehigher temperature upper portion of the plate will increase theresistance of the upper conductor more than the resistance of the lowerconductor will be increased, and accordingly the amperage of the. upperconductor will decrease and less wattage will be developed in conductor2 than in conductor 3. Since the voltage across the top half of theplate and the voltage across the bottom half are each equal to the linevoltage, the wattage input at the lower half of the plate is notdecreased so much as in present heaters with a single conductor wherethe voltage drop across the lower half is directly proportioned to theresistance of the lower half and is less than the line voltage for thenew plate. Consequently, the temperature of the lower half of the newplate will remain higher than heretofore. At the same time, due to thefact that the line voltage for the new plate is less than the voltagedrop across the top half of a plate that is provided with a singleconductor heating element and that develops approximately the same totalwattage, the maximum temperature. reached by the upper half of my platewill be less than in the case of the single conductor plate. The resultis that the maximum temperature at the hottest spot of my plate and theaverage temperature of the top half of the plate will be reduced ascompared with a .plate provided with a conventional single conductorheating element, but the average temperature of the lower half of theplate will not be reduced so much as formerly. This means that the totaltemperature difference over the plate will be reduced materially ascompared with a plate having only a single conductor heating element.More uniform heat distribution over the plate results in less expansionstress and a more durable plate from the breakage standpoint. Althoughthis heater can take the same wattage as heretofore and yet have a lowertemperature at its hottest spot, it also can take a higher wattagewithout exceeding the maximum temperature reached on the standard seriesdesign of heater. In an actual case the maximum temperature of theheater was lowered F. in one instance, and in the other instance therated wattage of the heater was increased about 180 watts.

Due to the fact that glass becomes a poorer insulator as it becomeshotter, it is advantageous to avoid high voltage differences betweenconductor bars in the hottest areas of the plate, as far as possible.The circuit design shown in Fig. 1 has such an advantage, as well as theadvantage of symmetry of pattern. However, other designs or patterns canbe used, such as shown in Figs. 2 to 5.

Thus, in Fig. 2 upper conductor [2 is arranged substantially like.conductor 2 of Fig. l, but lower conductor I3 is perfectly symmetrical,with everything below the top bar extending from the center of the platetoward its opposite ends.

In Fig. 3 the lower conductor 23 is arranged like conductor 3 of Fig. 1,and upper conductor 22 is more like conductor 12 of Fig. 2.

Fig. 4 shows a circuit pattern in which upper and lower conductors 32and 33 correspond, respectively, to upper conductor 23 of Fig. 3 and tolower conductor I3 of Fig. 2. Both conductors are symmetricallyarranged.

In Fig. 5 the lengths or bars formed from the zigzag portions of the twoconductors 42 and 53 extend vertically. The two conductors formsymmetrical patterns.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element on the plate, said element beingformed from a plurality of electrical conductors connected in parallelbetween said terminals, said conductors having substantially the sameresistance when cold but having greatly increased resistance when hot,each of said conductors covering a different area of said plate, andsaid areas being disposed one above the other, whereby the resistance ofthe upper conductor will be increased by heat rising from the lowerconductor.

2. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element on the plate, said element beingformed from two aluminum electrical conductors connected in parallelbetween said terminals and having substantially the same resistance whencold, one of the conductors covering substantially the upper half ofsaid plate, and the other conductor covering only the lower half of theplate, whereby heat rising from the lower conductor will increase thetemperature and resistance of the upper conductor.

3. An electric resistance heater comprisin an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the center of the bottomof the plate, said element being formed from two aluminum electricalconductors connected in parallel between said terminals, one of saidconductors coveringsubstantially the upper half of said plate, and theother conductor covering only the lower half of the plate.

4. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the center of the bottomof the plate, said element being formed from two aluminum electricalconductors connected in parallel between said terminals, one of theconductors covering substantially the upper half of said plate andhaving end portions extending down the ends of the plate and then acrossits bottom to said terminals, and the other conductor covering the areaof the plate bounded by the upper conductor portions and the portionjoining their upper ends.

5. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the center of the bottomof the plate, said element being formed from two aluminum electricalconductors connected in parallel between said terminals, one of theconductors extending from one of the terminals along the bottom of theplate to and then up along the end of the plate to and across its topand then back and forth across the plate in vertically spaced lengths tocover substantially its upper half, the conductor then extendingdownward along the other end of the plate to and along its bottom to theother terminal, and the other conductor covering the area of the platesurrounded by the upper conductor.

6. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the bottom of the plate,said element being formed from two aluminum electrical conductorsconnected in parallel between said terminals, one of said conductorsextending from one of the terminals along the bottom of the plate to andthen up along the end of the plate to and across its top and then backand forth across the plate in vertically spaced lengths to coversubstantially its upper half, the conductor then extending downwardalong the other end of the plate to the other terminal, and the otherconductor extending from one of the terminals back and forth across theplate in vertically spaced lengths to a point adjacent the lowest lengthof the first conductor and then downward beside the first conductor andfinally back to the other terminal.

7. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the center of the bottomof the plate, said element being formed from two aluminum lectricalconductors connected in parallel between said terminals, one of theconductors extending from one of the terminals along the bottom of theplate to and then up along the end of the plate to and across its topand then back and forth across the plate in vertically spaced lengths tocover substantially its upper half, the conductor then extendin downwardalong the other end of the plate to and along its bottom to the otherterminal, and the other conductor extending from the right hand terminalback and forth across substantially the right hand half of the plate in6 vertically spaced lengths and then across substantially the left handhalf of the plate directly below the lowest length of the upperconductor, the lower conductor then extending back and forth across saidleft hand half in vertically spaced lengths to the left hand terminal.

8. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted on the plate, said elementbeing formed from two aluminum electrical conductors connected inparallel between said terminals, one of said conductors COVSIiIlgsubstantially the upper half of said plate, and the other conductorcovering only the lower half of the plate, each conductor havingvertically spaced lengths extending back and forth across the plate frompoints near th ver tical center line of the plate to points near itsopposite ends.

9. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the bottom of the plate,said element being formed from two aluminum electrical conductorsconnected in parallel between said terminals, one of said conductorsextending from said terminals about half way up the opposite ends of theplate and then back and forth across the plate from said ends to pointsadjacent its vertical center line in vertically spaced lengths connectedat the top of the plate by a length extending nearly the full length ofthe plate, and the other conductor extending from one of the terminalsback and forth across the plate in vertically spaced lengths to a pointdirectly below said lengths of the other conductor and then downwardbeside the first conductor and finally back to the other terminal.

10. An electric resistance heater comprising an upright glass plate, aheating element covering most of one side of the plate, and a pair ofelectric terminals for said element mounted at the center of the bottomof the plate, said element being formed from two aluminum electricalconductors connected in parallel between said terminals, one of saidconductors extending from said terminals outward toward the oppositeends' of the plate and then upward to its top and up and down acrosssubstantially the upper half of the plate in horizontally spacedlengths, and the other conductor forming substantially the same patternover the lower half of the plate.

THEODORE W. GLYNN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,957,227 Reimers et a1 May 1,1934 2,119,680 Long June 7, 1938

